There are numerous chain saw sharpening guides disclosed in the patent literature and most of these chain saw sharpening guides are made of pressed metal which require many different formations, bendings and cuttings of the metal and they are of fixed design. Moreover, these are not very accurate. The various arcs of chain bars require that a gauge be adjustable for maximum cut of the chain matched to the arc of a particular bar.
Moreover, chain saws cut with alternate teeth on the right and left sides of the chain. The tooth that precedes the raker (also called the gauge) teeth or depth gauge has more bearing on the cut of the tooth behind the raker then does the tooth on the opposite side of the claim. The present invention is designed to skip the tooth on the opposite side end engage the next tooth on the same side. However, the invention can be used to check the tooth on the opposite side at the same time; the readings will not be the same due to the arc of the bar. Finally, the invention provides a gauge which will accurately measure the length of each cutting tooth.
According to the invention, a chain saw sharpening guide is comprised of an elongated flat metal plate body member having a thickness of about 1/8" to about 1/4", preferably about 3/16 of an inch thick which has smooth planar upper and lower surfaces. This elongated flat metal plate body member has a length spanning at least the distance between three consecutive teeth on a chain saw so that the ends of the flat metal plate member rests on two consecutive teeth which are on the same side of the chain. A cut-out space or notch is formed on one long side of the elongated flat plate metal body member to permit the plate to rest on two consecutive teeth on the same side of the chain saw with their intervening tooth on the opposite side projecting upwardly freely into the notch or cut-out space. A calibrated screw is threadably engaged in threaded bore passing through the plate with the projecting end of the calibrated screw engaging the gauge or raker tooth. Calibration markings uniformly dispersed around the threaded bore on the upper surface of the plate provides an indication in thousandths-of-an-inch of the distance that the calibrated screw projects below the lower surface of the flat metal plate body member and into engagement with the gauge tooth to thereby provide an easy adjustable gauge for measuring the raker or gauge tooth.
A notch or cut-out is also provided on one end of the elongated plate member and an arm is pivotally mounted on the bar so that it projects beyond the one side of the edge and into the notch so that it can measure the length of a saw tooth between the arm and the edge of the notch.
Thus, the invention provides a chain saw sharpening guide which enables the raker or gauge teeth to be set at a proper height for maximum cut of the teeth. In tests of a new chain off the shelf. The chain saw will make cuts at a certain rate of speed. The same chain on the same saw making the same cut will cut faster after having been adjusted with the gauge of the present invention.
Most saw shops reject chains when the teeth have been sharpened back to about half of their original length. With the gauge according to the present invention a chain can be sharpened to where it has had its teeth filed back until they are almost gone. As noted above, with this gauge, the time of the cut can be shortened, thereby saving fuel and wear and tear on the engine and the chain bar and lengthening the life of the chain and saving labor thereby being more economical to use. The chain saw gauge of the present invention has a sun burst angle gauge of from 0 to 35 degrees projecting either the right or left for accurate tooth angles in increments of 5 degrees. This allow for different filing tooth angles needed by different chains and for different chain sawing applications.